Toxicity of photoisomers of cyclodienes, namely, photoheptachlor, photoendrin, cis-photochlordane and the photolysis product of methoxychlor will be evaluated against aquatic and terrestrial invertebrate and vertebrate foodchain organisms. The in vivo metabolism and the identification of metabolites of these (and those of photodieldrin and photoisodrin, currently investigated) will be carried out in houseflies, fish and rat, followed by their in vitro metabolism by the mixed-function-oxidase, epoxide hydrase and glutathine-S-epoxide transferases of these animals. Water solubility, partition coefficients, and pick-up and elimination of these compounds by food-web and foodchain organisms will be followed by their biological concentration in a small model foodchain. These studies will evaluate the possible ecological and health hazards related with the toxicity "biological-magnification", "biological-concentration" and metabolism of these toxicants.